The heading of Class 4.1 covers flammable substances and articles, desensitized explosives which are
solids according to subparagraph (a) of the definition "solid" in 1.2.1, self-reactive liquids or solids
and polymerizing substances..
The following are assigned to Class 4.1:
- readily flammable solid substances and articles (see paragraphs 18.104.22.168.3 to 22.214.171.124.8);
- self-reactive solids or liquids (see paragraphs 126.96.36.199.9 to 188.8.131.52.17);
- solid desensitized explosives (see 184.108.40.206.18);
- substances related to self-reactive substances (see 220.127.116.11.19);
- polymerizing substances (see 18.104.22.168.20 and 22.214.171.124.21).
The substances and articles of Class 4.1 are subdivided as follows:
F Flammable solids, without subsidiary risk:
F2 Organic, molten;
FO Flammable solids, oxidizing;
FT Flammable solids, toxic:
FT1 Organic, toxic;
FT2 Inorganic, toxic;
FC Flammable solids, corrosive:
FC1 Organic, corrosive;
FC2 Inorganic, corrosive;
D Solid desensitized explosives without subsidiary risk;
DT Solid desensitized explosives, toxic;
SR Self-reactive substances:
SR1 Not requiring temperature control;
SR2 Requiring temperature control.
PM Polymerizing substances
PM1 Not requiring temperature control;
PM2 Requiring temperature control.
Flammable solids Definition and properties
Flammable solids are readily combustible solids and solids which may cause fire through friction.
Readily combustible solids are powdered, granular, or pasty substances which are dangerous if they
can be easily ignited by brief contact with an ignition source, such as a burning match, and if the
flame spreads rapidly. The danger may come not only from the fire but also from toxic combustion
products. Metal powders are especially dangerous because of the difficulty of extinguishing a fire
since normal extinguishing agents such as carbon dioxide or water can increase the hazard.
Substances and articles classified as flammable solids of Class 4.1 are listed in Table A of Chapter
3.2. The assignment of organic substances and articles not mentioned by name in Table A of
Chapter 3.2 to the relevant entry of sub-section 126.96.36.199 in accordance with the provisions of Chapter
2.1 can be based on experience or on the results of the test procedures in accordance with Part III, subsection
33.2.1 of the Manual of Tests and Criteria. The assignment of inorganic substances not
mentioned by name shall be based on the results of the test procedures in accordance with Part III,
sub-section 33.2.1 of the Manual of Tests and Criteria; experience shall also be taken into account
when it leads to a more stringent assignment.
When substances not mentioned by name are assigned to one of the entries listed in 188.8.131.52 on the
basis of the test procedures in accordance with the Manual of Tests and Criteria, Part III, sub-section
33.2.1, the following criteria apply:
(a) With the exception of metal powders or powders of metal alloys, powdery, granular or pasty
substances shall be classified as readily flammable substances of Class 4.1 if they can be easily
ignited by brief contact with an ignition source (e.g. a burning match), or if, in the event of
ignition, the flame spreads rapidly, the burning time is less than 45 seconds for a measured
distance of 100 mm or the rate of burning is greater than 2.2 mm/s;
(b) Metal powders or powders of metal alloys shall be assigned to Class 4.1 if they can be ignited
by a flame and the reaction spreads over the whole length of the sample in 10 minutes or less.
Solids which may cause fire through friction shall be classified in Class 4.1 by analogy with existing
entries (e.g. matches) or in accordance with any appropriate special provision.
On the basis of the test procedure in accordance with the Manual of Tests and Criteria, Part III,
Section 33.2.1 and the criteria set out in 184.108.40.206.4 and 220.127.116.11.5, it may also be determined whether
the nature of a substance mentioned by name is such that the substance is not subject to the provisions
for this Class.
If substances of Class 4.1, as a result of admixtures, come into different categories of risk from those
to which the substances mentioned by name in Table A of Chapter 3.2 belong, these mixtures shall be
assigned to the entries to which they belong on the basis of their actual degree of danger.
NOTE: For the classification of solutions and mixtures (such as preparations and wastes), see also
Assignment of packing groups
Flammable solids classified under the various entries in Table A of Chapter 3.2 shall be assigned to
packing groups II or III on the basis of test procedures of the Manual of Tests and Criteria, Part III,
sub-section 33.2.1, in accordance with the following criteria:
(a) Readily flammable solids which, when tested, have a burning time of less than 45 seconds over
a measured distance of 100 mm shall be assigned to:
Packing group II: if the flame passes the wetted zone;
Packing group III: if the wetted zone stops the flame for at least four minutes;
(b) Metal powders or powders of metal alloys shall be assigned to:
Packing group II: if, when tested, the reaction spreads over the whole length of the sample
in five minutes or less;
Packing group III: if, when tested, the reaction spreads over the whole length of the sample
in more than five minutes.
For solids which may cause fire through friction, the packing group shall be assigned by analogy with
existing entries or in accordance with any special provision.
Self-reactive substances Definitions
For the purposes of ADR, self-reactive substances are thermally unstable substances liable to undergo
a strongly exothermic decomposition even without participation of oxygen (air). Substances are not
considered to be self-reactive substances of Class 4.1, if:
(a) they are explosives according to the criteria of Class 1;
(b) they are oxidizing substances according to the classification procedure for Class 5.1
(see 18.104.22.168) except that mixtures of oxidizing substances which contain 5% or more of
combustible organic substances shall be subjected to the classification procedure defined in
(c) they are organic peroxides according to the criteria of Class 5.2 (see 22.214.171.124);
(d) their heat of decomposition is less than 300 J/g; or
(e) their self-accelerating decomposition temperature (SADT) (see Note 3 below) is greater than
75 °C for a 50 kg package.
NOTE 1: The heat of decomposition can be determined using any internationally recognised method
e.g. differential scanning calorimetry and adiabatic calorimetry.
NOTE 2: Mixtures of oxidizing substances meeting the criteria of Class 5.1 which contain 5% or
more of combustible organic substances, which do not meet the criteria mentioned in (a), (c), (d) or
(e) above, shall be subjected to the self-reactive substance classification procedure.
A mixture showing the properties of a self-reactive substance, type B to F, shall be classified as a selfreactive
substance of Class 4.1.
A mixture showing the properties of a self-reactive substance, type G, according to the principle given
in section 20.4.3 (g) of Part II of the Manual of Tests and Criteria shall be considered for
classification as a substance of Class 5.1 (see 126.96.36.199).
NOTE 3: The self-accelerating decomposition temperature (SADT) is the lowest temperature at which
self-accelerating decomposition may occur with a substance in the packaging as used during
carriage. Requirements for the determination of the SADT are given in the Manual of Tests and
Criteria, Part II, Chapter 20 and section 28.4.
NOTE 4: Any substance which shows the properties of a self-reactive substance shall be classified as
such, even if this substance gives a positive test result according to 188.8.131.52.5 for inclusion in
The decomposition of self-reactive substances can be initiated by heat, contact with catalytic
impurities (e.g. acids, heavy-metal compounds, bases), friction or impact. The rate of decomposition
increases with temperature and varies with the substance. Decomposition, particularly if no ignition
occurs, may result in the evolution of toxic gases or vapours. For certain self-reactive substances, the
temperature shall be controlled. Some self-reactive substances may decompose explosively,
particularly if confined. This characteristic may be modified by the addition of diluents or by the use
of appropriate packagings. Certain self-reactive substances burn vigorously. Self-reactive substances
are, for example, some compounds of the types listed below:
aliphatic azo compounds (-C-N=N-C-);
organic azides (-C-N3);
diazonium salts (-CN2
N-nitroso compounds (-N-N=O); and
aromatic sulphohydrazides (-SO2-NH-NH2).
This list is not exhaustive and substances with other reactive groups and some mixtures of substances
may have similar properties.
Self-reactive substances are classified into seven types according to the degree of danger they present.
The types of self-reactive substances range from type A, which is not accepted for carriage in the
packaging in which it is tested, to type G, which is not subject to the provisions for self-reactive
substances of Class 4.1. The classification of types B to F is directly related to the maximum quantity
allowed in one packaging. The principles to be applied for classification as well as the applicable
classification procedures, test methods and criteria and an example of a suitable test report are given
in Part II of the Manual of Tests and Criteria.
Self-reactive substances which have already been classified and are already permitted for carriage in
packagings are listed in 184.108.40.206, those already permitted for carriage in IBCs are listed in 220.127.116.11,
packing instruction IBC520 and those already permitted for carriage in tanks according to Chapter 4.2
are listed in 18.104.22.168, portable tank instruction T23. Each permitted substance listed is assigned to a
generic entry of Table A of Chapter 3.2 (UN Nos. 3221 to 3240), and appropriate subsidiary risks and
remarks providing relevant transport information are given.
The collective entries specify:
- self-reactive substances types B to F, see 22.214.171.124.11 above;
- physical state (liquid/solid); and
- temperature control (when required), see 126.96.36.199.17 below.
The classification of the self-reactive substances listed in 188.8.131.52 is based on the technically pure
substance (except where a concentration of less than 100% is specified).
Classification of self-reactive substances not listed in 184.108.40.206, 220.127.116.11, packing instruction IBC520 or
18.104.22.168, portable tank instruction T23 and assignment to a collective entry shall be made by the
competent authority of the country of origin on the basis of a test report. The statement of approval
shall contain the classification and the relevant conditions of carriage. If the country of origin is not a
Contracting Party to ADR, the classification and the conditions of carriage shall be recognized by the
competent authority of the first country Contracting Party to ADR reached by the consignment.
Activators, such as zinc compounds, may be added to some self-reactive substances to change their
reactivity. Depending on both the type and the concentration of the activator, this may result in a
decrease in thermal stability and a change in explosive properties. If either of these properties is
altered, the new formulation shall be assessed in accordance with the classification procedure.